In the manufacture of integrated circuit wafers and other devices, such as disks for CDs and computer hard disk drives, methods and apparatus have been developed for effecting the manufacture of the integrated circuit wafers and other devices in ultra-clean environments as free as possible from any source of contamination that might adhere to the semiconductor wafer or other such devices. It has been found that these essentially sterile conditions can best be achieved by manufacturing these devices, including IC wafers, in xe2x80x9cclean roomsxe2x80x9d where semiconductor-wafers of various sizes, e.g., 4,6, 8 and 12 in. in diameter are processed, these devices and wafers having various thicknesses averaging about 0.030xe2x80x3 and being flat to very close tolerances. In the case of semiconductor wafers, each contains a multiplicity of independent integrated circuits or xe2x80x9cchipsxe2x80x9d embedded therein, and the wafers are preferably handled in their wafer-form to efficiently effect the mass production and testing of the independent integrated circuits imbedded therein.
It is in this handling and manipulation of the completed wafers or other devices where the specter of contamination from an outside source frequently arises. Ideally, each wafer or other device would be moved or transferred from one location to another, during manufacture and thereafter, without having its top or bottom surfaces touched by any means, human or mechanical, this to prevent contamination of the top and bottom surfaces of the wafer. Accordingly, one of the principal objects of the present invention is the provision of a method and apparatus or device that may be selectively attached to and detached from an integrated circuit wafer or other device without contaminating the sensitive active areas of the surfaces of the wafer or other device.
One of the conventional methods for handling integrated circuit wafers is the use of an xe2x80x9cend-effecterxe2x80x9d that comprises an arm attached at its proximal end to a robotic manipulation mechanism and the source of negative pressure, i.e., a vacuum source. A channel is formed in the end defector, with the proximal end of the channel communicating with the vacuum source while the distal end of the channel opens onto a top surface on or near the distal end of the arm that abuts against the bottom side of the wafer, the wafer thus being et xe2x80x9csuckedxe2x80x9d or drawn against the top surface of the end-effector by the negative or xe2x80x9cvacuumxe2x80x9d pressure imposed on the bottom surface of the wafer. Much development effort has been expended to develop various types of structures that utilize this method of attachment of a manipulation arm or xe2x80x9cend-defectorxe2x80x9d to the underside of an integrated circuit wafer, and numerous patents have issued illustrating and describing these types of devices. A sampling of these types of patent is as follows:
However, such development efforts have not overcome the fact that the top surface of the end-effector that touches the wafer, top or bottom surface, may itself be contaminated and that such contamination may be transferred to the wafer. Another disadvantage of the vacuum clamping type of end-effecter wafer handling system is the risk of an interruption of the vacuum pumping system resulting from a power failure or a vacuum system leak that could cause disengagement of the wafer from the end-effector with consequent loss of the wafer through displacement laterally or vertically, with attendant striking of adjacent structures by the wafer, resulting in chipping or shattering of the wafer.
Much development effort has been expended to mitigate the disadvantages of end-effectors that utilize vacuum engagement end-effectors, and this development effort has generally been directed to the design of devices that operate by grasping the wafer in a manner to impose radially directed forces on the circumferential peripheral edge of the wafer, i.e., forces imposed in a direction perpendicular to the central axis of the wafer. A sampling of devices utilizing this method of grasping a wafer may be found in the following United States patents:
The patents listed above have resulted from a preliminary patentability and novelty search, and it appears that all of these patents are directed to the concept of the imposition of a radially inwardly directed force on the circumferential peripheral edge of the wafer.
Accordingly, another principal object of the present invention is the provision of a method and apparatus for gripping or grasping of an arcuate xe2x80x9cfree-zonexe2x80x9d extending radially inwardly from a peripheral edge of a wafer by the imposition of a gripping force directed perpendicularly to the flat surface of the wafer or, stated in other words, by a gripping force imposed on an arcuate peripheral xe2x80x9cfee-zonexe2x80x9d surface portion of the wafer in a direction parallel to the central axis of the wafer, i.e., perpendicular to the xe2x80x9cfree-zonexe2x80x9d surface portion of the wafer.
Another object to the present invention is the provision of an end-effector that eliminates the use of negative pressure or xe2x80x9cvacuumxe2x80x9d to engage itself to an integrated circuit wafer via surface contact as occurs with end-effectors that utilize the vacuum engagement principle and instead utilizes positive or negative pressure to activate a mechanism that grasps or releases the wafer in a non-active arcuate peripheral xe2x80x9cFree-zonexe2x80x9d or area.
A still further object of the invention is the provision of an end-defector device that utilizes fail-safe positive pressure to effect selective clamping or release of a wafer gripped by the end effecter so that the WAFER remains gripped by the end effecter even in the event of equipment failure.
Integrated circuit wafers may intentionally be manufactured with a xe2x80x9cnon-intrusionxe2x80x9d area surrounded by a peripheral xe2x80x9cfree zonexe2x80x9d of selected width of about 2 mm that is not occupied by it or used for the formation of integrated circuits in the wafer. It is important that this peripheral xe2x80x9cfree-zonexe2x80x9d be as narrow as possible so as to maximize the number of integrated circuits that are formed in the xe2x80x9cnon-intrusionxe2x80x9d area of the wafer.
Accordingly, it is yet another object of the invention to provide an end-effecter operable to selectively grip a wafer by the deployment of a gripping device on the peripheral xe2x80x9cfree-zonexe2x80x9d of the wafer and the imposition of a sufficient gripping force applied perpendicularly to the top and bottom surfaces in the xe2x80x9cfree-zonexe2x80x9d to prevent inadvertent release of the wafer while responding to positioning commands and which remains responsive to selectively applicable positive or negative fluid pressure to cause or cancel the positive gripping force to thus selectively grip or release the wafer.
A still further object of the invention is the provision of an end-defector device incorporating means for selectively gripping and releasing a substantial arcuate surface portion of the peripheral xe2x80x9cfree-zonexe2x80x9d of an integrated circuit wafer on both top and bottom surfaces of the wafer surrounding the xe2x80x9cnon-intrusionxe2x80x9d area and without intrusion into the xe2x80x9cnon-intrusionxe2x80x9d area.
A still further object of the invention is the provision of an end-effector device for reliably gripping and effecting manipulation of an integrated circuit wafer without contact with the xe2x80x9cnon-intrusionxe2x80x9d surface areas of the wafer, and comprising a selectively adjustable arcuate socket for receiving the arcuate xe2x80x9cfree-zonexe2x80x9d of an integrated circuit wafer, the socket being actuable to an open condition for insertion of the wafer xe2x80x9cfree-zonexe2x80x9d thereinto, and thereafter being actuable to resiliently grip or clamp onto the arcuate xe2x80x9cfree-zonexe2x80x9d portion of the wafer to retain it gripped by the socket until selectively released therefrom.
A still further object of the invention is the provision of an end-effector device that is operable to selectively grip the arcuate peripheral xe2x80x9cfree-zonexe2x80x9d of the wafer at circumferentially spaced locations thereon.
Yet another object of the invention is the provision of an end-effector device controllable manually or automatically by a control system responsive to input from sensors to effect opening of the socket to receive an arcuate peripheral xe2x80x9cfree-zonexe2x80x9d of the wafer and to effect closing adjustment or clamping of the socket on the peripheral xe2x80x9cfree-zonexe2x80x9d when the arcuate peripheral xe2x80x9cfree-zonexe2x80x9d is properly inserted and seated in the socket.
The invention possesses other objects and features of advantage, some which, with the foregoing, will become apparent from the following description and the drawings. It is to be understood however that the invention is not limited to the embodiments illustrated and described since it may be embodied in various forms within the scope of the appended claims.
In terms of broad inclusion, the end-effector of the invention for grasping integrated circuit wafers comprises a talon-like device that effectively grips resiliently or otherwise, an arcuate peripheral xe2x80x9cfree-zonexe2x80x9d of the wafer to enable risk-free manipulation of the wafer in whatever direction is appropriate and without effecting contact of the wafer in a manner to contaminate it. The end-effector of the invention may selectively be used in opposed pairs to grip large wafers by their diametrically opposed arcuate peripheral xe2x80x9cfree-zonesxe2x80x9d or, preferably, may be used individually to grip a single arcuate peripheral xe2x80x9cfree-zonexe2x80x9d of a wafer. Structurally, in one aspect of the invention, the end-effector or talon-like device is formed by two confronting top and bottom plate members configured to form a xe2x80x9cshellxe2x80x9d within which or between which is displaceably mounted a member which, when selectively displaced in one direction by the imposition of an appropriate force, opens a normally closed gripping member for receiving the arcuate peripheral xe2x80x9cfree-zonexe2x80x9d of the wafer and when selectively displaced in the opposite direction by the removal of the opening force tightly grips the arcuate peripheral xe2x80x9cfree-zonexe2x80x9d of the wafer to releasably retain it attached to the end-effector, from which it may selectively be released by the imposition of force in an opening direction that opposes and overcomes the force that effects gripping of the wafer. It will of course be understood that the end-effector may be configured as a normally open device that is closed, i.e., by an appropriately directed force. Appropriate sensors, while not essential, are preferably provided to signal the proper positioning of the wafer in relation to the end-effector, and a control system may be provided responsive to the sensor signals to effect opening and closing operation of the arcuate talon-like socket or clamp.